application of surface geophysics to ground-water investigations

123 Pages·2001·9.87 MB·English

Techniques of Water-Resources Investigations
of the United States Geological Survey
CHAPTER Dl
APPLICATION OF SURFACE GEOPHYSICS
TO GROUND-WATER INVESTIGATIONS
By A. A. R. Zohdy, G. P. Eaton,
and D. R. Mabey
BOOK 2
COLLECTION OF ENVIRONMENTAL DATA
DEPARTMENT OF THE INTERIOR
MANUEL LUJAN, Jr., Secretary
U.S. GEOLOGICAL SURVEY
Dallas 1. Peck, Director
Any use of trade, product, of firm names in this publication is for
descriptive purposes only and does not imply endorsement by the
U.S. Government
First printing 1974
Second printing 1980
Third printing 1984
Fourth printing 1990
UNITED STATES GOVERNMENT PRINTING OFFICE: 1974
For sale by the Books and Open-File Reports Section, U.S. Geological Survey,
Federal Center, Box 25425, Denver, CO 80225
PREFACE
The series of manuals on techniques describes procedures for planning
and executing specialized work in water-resources investigations. The no
terial is grouped under major subject headings called “Books” and f,ur-
ther subdivided into sections and chapters. Section D of Book 2 is on sur-
face geophysical methods.
The unit of publication, the chapter, is limited to a narrow field of
subject matter. This format permits flexibility in revision and publication
as the need arises. “Application of surface geophysics to ground-water in-
vestigations” is the first chapter to be published under Section D of
Book 2.
X
CONTENTS
PUS
Abstract ________________________________ 1 Electrical methods-Continued
Introduction _____________________________ 1 Direct current-resistivitiy method-Continued
Design of geophysical surveys _________ 1 Analysis of electrical sounding curves-
Collection and reduction of geophysical Continued
data ______________________________ Quantitative interpretation-
Interpretation ---__-_--__---_-_-__--- Continued
The literature of exploration geophysics, Analytical methods of in-
Electrical methods, by A. A. R. Zohdy ___-_ terpretation-Continued
Telluric current method ______________ Three-layer interpre-
Magneto-telluric method ______________ tation _----- 42
Spontaneous polarisation and Four-layer (or more)
streaming potentials ___________- 8 interpretation ___- 44
Direct current-resistivity method ___-_ a Empirical and semi-empirical
Definition and units of resistivity -_ 8 methods of interpreta-
Rock resistivities _________________ 9 tion __- __-__-- -_- ----- 45
Principles of the resistivity method, 9 Moore’s cumulative red5
Electrode configuration --__--___-- 10 tivity method -_-__ --__- 45
Wenner array ------------.-,-- 10 Barnes’ layer method -__-- 46
Lee-partitioning array _--___-- 11 Applications of reeistivity surveys
Schlumberger array --------s 11 in ground-water studies ----- 47
Dipole-dipole arrays _____-____ 11 Mapping buried stream
Electrical sounding and horizontal channels ___________--_-_ 47
profiling _______________________ 13 Geothermal studies ---__----- 50
Comparison of Wenner, Schlum- Mapping fresh-salt water in-
berger, and dipole-dipole m-sure- terfaces ____-__--_---- 52
ments _________________________ 16 Mapping the water table ------ 54
Problem of defining probing depth,, 20 Mapping clay layers -_--_----- 55
Advantages of using logarithmic Electromagnetic methods ___--_-_---- - 56
coordinates ____________________ 20 Induced polarization methods --------- - 56
Geoelectric parameters __-_________ 22 Relationship between apparent
Types of electrical sounding curves chargeability and apparent IX?-
over horizontally stratified media- 24 sistivity ________-__-_---------- 61
Electrical sounding over laterally Induced polarization sounding and
inhomugeneous media ___________ 26 profiling __----_--------------- 61
Limitations of the resistivity method 27 Applications of induced polarization
Analysis of electrical sounding in ground-water surveys ---e--s 63
curves ---------------__------- 32 References cited ___________-_____-__- 63
Qualitative interpretation --e-e 33 Seismology, by G. P. Eaton __-_--____--_- 67
Determination and use of Elementary principles _---_---___----- 68
total transverse resist- Reflection versus refraction shooting _- 70
ance, T, from sounding Comparison of the refleotion and refrac-
curves -----L---m------- 34 tion seismic methods in practice ----- 72
Determination of total Seismic refraction measurement8 in
longitudinal conductance, hydrogeology ________-_____-_- - 73
S, from sounding curves- 36 Effect of departures from the simple
Determination of average stratified model _- _____--___ 73
longitudinal resistivity, The multilayered model _____-- 73
~1, from a Qounding Effect of a regular increase of
curve _-__----__- 36 velocity with depth ____--_- - 73
Distortion of sounding Effect of dipping layers _---_- 73
curves by extraneous Effect of a sloping ground
influences _______--___-- 37 surface _____-__-_---_--_-_- 75
Quantitative interpretation __- 39 Effect of a buried steplike re-
Analytical methods of in- fractor _____--_.-_---___-_- - 75
terpretation --mm_-- 39 Effect of a discordant steep
Two-layer interpreta- sided body -------------m-- 75
tion ______-_-__-- 41 Effect of a thin refractor ----- 76
V
VI
Seismology, by G. P. Baton-Continued Gravimetry-Continued
Seismic refraction measuremente Reduction of gravity data-Continued
in hydrogeology-Continued Terrain correction _____-__-_---- -- 92
Effect of departures from the Drift correction ___________ - --___ 93
simple stratified model-Continued Regional gradients ________------- 93
Effect of a velocity inversion at Bouguer anomaly ___________ -_--- 94
depth --------------------- 76 Interpretation of gravity data -___--- 94
Effect of a refractor of ir- Ambiguity __--------_--------_-- 94
regular conflguration ------ 76 Interpretation techniques. __- __-- - 97
Effect of lateral varying SigniAcance and use of den&y
velocities _____--__-_____ 76 meaeurements _-______-_- 97
Corrections applied to seismic refraction Application of gravimetry to hydra-
measurements ______________________ 76 geology _--------_ _------.-- 100
Elevation correction _-__--________-__- 77 Aquifer geometry _________..----- - 100
Weathered-layer correction ___________ 77 Estimating average total porosity 100
Surface method ___----..-- 100
Errors in seismic refraction measure
Borehole method __--..-- 104
ments _____________________________ 77
Effect of ground-water levels on
Application of seismic refraction meas-
gravity readings ________..------ 105
urements in hydrogeology _____- 79
References cited ____------e-m’ m..----m - 106
Mapping buried channels _________ 79
Magnetic methods, by D. R. Mabey _..--- 107
Measuring depths to the water table 80
Magnetic surveys ________-----.- 108
Determining the groee stratigraphy
Magnetic properties ________-_-..-- 109
of an aquifer __________________ 81
Design of magnetic surveys _-_.._-- - 109
Mapping lateral facies variations in
Data reduction _____-_- -----m-.m------ 110
an aquifer _____________________ 82
Interpretation of magnetic data ._---- 110
Estimating porosity from seismic
Examplee of magnetic surveye _.------- 111
wave-velocity values _~~_~~~~~~~~ 83
Gem Valley, Idaho _____-__-__-_--- 111
References cited _____________________ 84 Antelope Valley, California .----- 113
Gravimetry, by G. P. Eaton __-_--------- 85 References cited _____________-.-_---- - 116
Reduction of gravity data ___________- Cost of geophysical surveys in 1970 ._----- 116
Latitude correction ________-_____- 89 Electrical methods ______________-__-- 116
Tidal correction __-_-------------- 89 Gravity surveys __________-___.-____-- 116
Altitude corrections _----_------- - 89 Seismic surveys. _________________--_-- 116
Free-air correction __-__-_--- 90 Magrmtic surveys _____________,._____ - 116
Bouguer correction __-_--__--- 90
FIGURES
1. Diagram showing flow of telluric currant over an anticline _---- -__---------------_--~------- 6
2. Examples of electrode arrays for measuring 1~and y components of telluric fleld ------..------- 6
3. Telluric map of the Aquitaine basin, France _____________________ -_---_-------------.-------- 7
4. Diagram showing the relationship between a point source of current 2 (at origin of coordi-
nates) in an isotropic med.ium of resistivity p and the potential V at any point P ---_------ 9
5. Wenner, Lee-partitioning, and Schlumberger electrode arrays __---___--_____--------~------- 11
6. Dipole-dipole arrays ________ ____________________----------------------------------~-------- 12
7. Graph showing horizontal proAle and interpretations over a shallow gravel deposit in California
using Wenner array _______________________________ ------_-_---------------------.-------- 14
8. Map of apparent resistivity near Campbell, Calif -_----__-________-__----------------------- 15
9. Graph showing horisontkl profiles over a buried stream channel ueing two electrode spacings:
a = 30 feet and a = 60 feet __-_______________-___-------------------------------------- 16
10. Electrode arrays ___-________________----------------------------------------------------- 17
11. Graph showing comparison between four-layer Schlumberger and Wenner sounding CUNea 18
12. Correct displacements on a Schlumberger sounding curve and method of smoothing _---------- 19
13. Logarithmic plot of sounding curves _____-________-__-__------------------------------------ 21
14. Linear plot of sounding curves ------__-_---____-_------- -_-----__-_____------------------- 22
15. Columnar prism used in deflning geoelectric parameters of a section __-__-__-------_--------- 23
CONTENTS VII
16. Comparison between two-layer Schlumberger cm for pdp = 10 and O.l;h = 1 meter for
both curves ___________________-________________ ____________________-------------------- 25
1’7. Comparison between two-layer azimuthal (or equatorial) and radial (or polar) soundiig CUFV~B 26
18. Examples of the four types of three-layer Schlumberger sounding curves for three-layer Earth
models ________________________________________- 27
19. Examples of three of the eight posible types of Schlumberger sounding curves for four-layer
Earth models ____________________________ __________-___--__---------------------------- 28
20. Examples of the variation of Schlumberger sounding curves across a vertical contact at variou8
azimuths ________________________________________--------------------------------------- 29
21. Examples of the variation of Winner sounding curves across a vertical contact at various azi-
muths ___________-_______________________c____- SO
22. Examples of diferent types of cusrve equivalence ____---------------------------------------- 31
23. Map of apparent resistivity near Rome, Italy __-___------- ---__---------------------------- 33
24. Sections of apparent reaistivity near Minidoka, Idaho. Values on contour lines designate apparent
resistivities in ohm-meters. Snake River basalt ,thickens toward the north --------------- 34
25. Graphical determination of total transverse resistance from a K-type, Schlumberger sound-
ing curve __-_____-_____-_____- 35
26. Profile of total transverse resistance values T in ohm-meters squared, near Minidoka, Idaho -- 36
27. Graphical determination of total longitudinal conductance S from an H-type Schlumberger
sounding curve ____________________-__- 37
28. Transformation of a Schlumberger KH-type curve into ‘a polar dipole-dipole curve to evaluate
P’nln = pi and H = SpL ________________________________________------------------------ 38
29. Distortion of sounding cures by cusps caused by lateral inhomogeneities ------------------ 39
30. Example ‘of a narrow peak on a K-type curve, caused by the limited lateral extent of a resistive
middle layer ____-___________-_______________________------------------------------------ 40
31. Example of a distorted HK-Schlumberger curve and the method of correction ------------_____ 41
32. Examples of discontinuities on Schlumherger curves caused by a near vertical, dikelike structure _ 42
33. Two-layer master set of sounding CUNeS for the Schlumberger array -_-------_----_______ 43
34. Interpretation of a two-layer Schlumberger curve (p/p = 5) ---------------------------- 44
35. Interpretation of a three-layer Schlumberger H-type curve __________________________________ 46
36. Interpretation of a four-layer Schlumberger curve by the auxiliary point method using ,two
three-layer curves ________________________________________----------------------------- 46
37. Map of San Jose area, California, showing areaa studied __________________________________ 48
38. Map of apparent resistivity in Penitencia area., California ___________________________________ 49
39. Resistivity profile and geologic section, Penitencia, Calif ____________________________________ 50
40. Map of apparent resiativity near Campbell, Calif., obtained with Wane, array at a P 30
feet and showing location of Section AA’ ________________________________________------- 61
41. Geoelectric section and drilling results near Campbell, Calif ___________________________________ 52
42. Apparent .resistivity profile and geologic interpretation over buried channel, near Salisbury, Md - 53
43. Buried stream channel near Bremerhaven, West Germany, mapped from electric sounding
(after Halenbach, 1953) ___________-______-_____________________--~-------------------- 64
44. Map of apparent reaistivity in the Bad-Krozingen geothermal area, Germany ________________ 56
45. Map of apparent resistivity in geothermal areas in New Zealand ____ - ________________________ 66
46. Map of apparent resisbivity in White Sands area, New Mexico. for electrode a_p acing- AB/2 =
1,000 feet ____-__-__-__- 67
47. Map of White Sands area, New Mexico, showing isobaths of the lower surface of fresh-water
aquifer __----__-__-__-__-____---------------------------------------------------------- 58
48. Examples of Schlumberger sounding curves obtained in the Wmhite Sands area, New Mexico ___ 59
49. Block diagram of Pohakuloa-Humuula area, Hawaii ________________________________________-- 59
50. Geoelectric section north of Bowie, Ariz. ________________ - __________________________________ 60
51. Examples of Schlumberger sounding cures obtained near Bowie, Ariz ________________________ 60
52. Apparent resistivity and apparent chargeability IP sounding curves for a four-layer model ----- 61
53. G-eoelectric Section, VES and IP sounding cures of alluvial deposits in Crimea --------------- 62
54. Schematic ray-path diagram for seismic energy generated at source S and picked up at geophone
G ________________________________________------------------------------- -- ---- -- ----- - 69
55. Huygens’ construction for a head wave generated at the VI-V2 interface ____--- ---- ----------- 70
56. Seismic wave fronts and traveltime plot for an idealized horizontally layered model ----------- 71
57. Schematic traveltime curves for idealized nonhomogeneous geologic models ---------------- 74
VIII CONTENTS
68. Comparison of 9’7 seismic refraction depth determinations versus drill-hole depths at the same lo-
calities _______ ____ _--_----____-_____--_--------------------------------------------- ---- 78
69. Seismic cross section, drill-hole data, and traveltime curves for a buried Tertiary stream dhannel
in northern Nevada County, Calif ____________________------------------~---------------- 79
60. Structure contours on the buried bedrock surface of the Passaic River Valley, northern New Jer-
sey, based on seismic refraction and drill-hole measurements ____________________________ 80
61. Seismic cross se&ion of the Jordan Valley ea& of Great Salt Lake, Utah ----_--------------~ 81
62. Distribution of observed compressional wave velocities in unsaturated sediments of the ancestral
Miami River Valley, Ohio ___-__-___ ____________________--------------------------------- 82
63. Plot of observed porosity versus compressimal wave velocity for unconsolidated sedimerrts ____ 83
64. Gravitational attraotion at point P due to buried mass dm _____-_______------_______ - ---- - 86
86. A, Observed gravity profile for a buried sphere in a homogeneous rigid nonrotating Earth. B,
Sources of variation present in gravitational measurements made in the search for a buried
sphere in a schematic, but real, Earth model ____________________-----------------.~------ 88
66. Bouguer gravity profiles across a low ridge based on six different densities employed in calcu-
lating the Bouguer correction ___________________________ - _______________________________ 91
67. Schematic models and associated Bouguer gravity anomalies for idealized geologic bodie,s ____- 96
68. Plot of observed compressional wave velocities versus density for sediments and sedimentary rocks 99
69. A, Complete Bouguer-gravity map of a buried pre-glacial channel of the Connecticut River. B,
Complete Bouguer-gravity map of part of San Georgonio Pass, Calif _____________._______ 101
70. A, Distribution of outcrops and structure contours on the buried bedrock surface, Perris Valley,
Calif. B, Bouguer-gravity map of Perris Valley, Calif _________-___ - __________ - ___________ 102
71. Profiles of observed Bouguer gravity, residual gravity, and calculated porosity for Perris Valley,
,Calif ________________________________________------------------------------------------ 103
72. In situ density log determined with a borehole gravity meter: drill hole UCe-18, Hot Creek Val-
by, Nev ________________________________________---------------------------------------- 104
73. Plots of gravity values versus depth to the water table for aquifers having a porosity of 33
percent and specific retentions of 0 percent and 20 percent, respectively ___-- ______-_----- 106
74. Aeromagnetic profile at 230 m above Gem Valley, Idaho __-__-__-________-__--------------- 112
76. Aeromagnetic map of Gem Valley and adjoining areas, Idaho _________--_____________________ 114
76. Gravity and aeroma8netic profiles acrose Cenozoic basin in Antelope Valley, Calif __________- 116
Metric Units of Measurement
Many of the analyses and compilations in this report were made in
metric unite of measurements. The equivalent English units are given
in the text and illustrations where appropriate. To convert metric units
to English units, the following conversion factors should be used:
Mebrie units
Length in centimeters (cm) ___---------- x0.394 = inches
in meters (m) ____ ----_- __________ X 3.281 -feet
in kilometers (km) ______________ X 0.6214 =miles
Area in square kilometers (km*) _____-_-- x 0.386 = square miles
Slope in meters per kilometer (m/km) ---- X6.28 =feet per imile
APPLICATION OF SURFACE GEOPHYSICS
TO GROUND-WATE.RINVESTIGATIONS
By A. A. R. Zohdy, C. P. Eaton, and D. R. Mabey
Abstract applications and interpretation in selected geohydro-
logic environments.
This manual reviews the standard methods of sur-
The objective of the manual is to provide the hy-
face geophysics applicable to ground-water investi- drogeologist with a sufficient understanding of the
gations. It covers electrical methods, seismic and
capabilities, limitations, and relative cost of gee-
gravity methods, and magnetic methods.
nhvsical methods to make sound decisions as to
The general physical principles underlying each ah-& use of these methods is desirable. The manual
method and its capabilities and limitations are’ de- also provides enough information for the hydrogeolo-
scribed. Possibilities for non-uniqueness of interpre- gist to work with a geophysicist in designing geophys-
tation of geophysical results are noted. Examples ical surveys that differentiate. significant hydro-
of actual use of the methods are given to illustrate geologic changes.
Introduction
This manual is a brief review of the stage of development and testing ; thus,
standard methods of surface geophysical ex- their eventual importance cannot be ap-
ploration and their application in ground- praised at this time. Borehole geophysical
water investigations. It explains the capabili- techniques will not be discussed here except
ties of exploration geophysics and, in a gen- as they relate to surface or airborne sur-
eral way, the methods of obtaining, process- veys.
ing, and interpreting geophysical data. A In the discussions that follow each of the
minimum of mathematics is employed, and major geophysical methods will be briefly
the scopeis limited to an elementary discus- described with emphasis on the applications
sion of theory, a description of the methods, and limitations in ground-water investiga-
and examples of their applications. It is in tions. A few examples of successful applica-
no sense intended as a textbook on applied tion of each method will be described.
geophysics. Rather its aim is to provide the
hydrogeologist with a rudimentary under-
standing of how surface geophysical meas-
Design of Geophysical
urements may be of help to him. Many of
the standard methods of geophysical explora- Surveys
tion are described, but those used most ex-
tensively in ground-water investigations Geophysical surveys can be useful in the
are stressed. The rapidly developing tech- study of most subsurface geologic problems.
niques of geophysical exploration involving Geophysics also can contribute to many in-
measurements in the microwave, infrared, vestigations that are concerned primarily
and ultraviolet portions of the electro- with surface geology. However, geophysical
magnetic spectrum are not included. The ap- surveys are not always the most effective
plication of these “remote sensors” to method of obtaining the information needed.
ground-water investigations is in an early For example, in some areas auger or drill
1
2 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS
holes may be a more effective way of obtain-
Interpretation
ing near-surface information than geophysi-
cal surveys. In some investigations a com-
Interpretation of geophysical data can be
bination of drilling and geophysical meas-
completely objective or highly subjective. It
urements may provide the optimum cost-
can range from a simple inspection of a map
benefit ratio. Geophysical surveys are not
or profile to a highly sophisticated operation
practical in all ground-water investigations,
involving skilled personnel and elaborate
but this determination usually can be made
supporting equipment. Some interpretations
only by someone with an understanding of
require little understanding of the geology,
the capabilities, limitations, and costs of
but the quality of most interpretations is im-
geophysical surveys.
proved if the interpreter has a good under-
A clear definition of the geologic or hydro-
standing of the geology involved. Although
logic problem and objectives of an investiga-
some individuals are both skilled geophysi-
tion is important in determining w,hether
cists and geologists, a cooperative effort be-
exploration geophysics should be used and
tween geologists and geophysicists is usually
also in designing the geophysical survey. The
the most effective approach to the interpreta-
lack of a clear definition of the problem can
tion of geophysical data.
result in ineffective use of geophysical
methods. The proper design of a geophysical
survey is important not only in insuring that
The Literature of
the needed data will be obtained but also in
controlling costs, as the expense of making Exploration Geophysics
a geophysical survey is determined primarily
by the detail and accuracy required.
The science, technology, and art of geo-
physical exploration have undergone explo-
sive growth in the last two decades and with
Collection and Reduction of
this growth has come an increasing degree
of specialization in all subdisciplines of the
Geophysical Dato
field. The literature indicates an increasing
trend in this direction and the geologist or
Some simple geophysical surveys can be
engineer interested in applications of geo-
made by individuals with little previous ex-
physics to problems with which he is con-
perience and with an investment in equip-
cerned is faced with a growing array of books
ment of only a few hundred dollars. Other
and periodicals. With the idea that interested
surveys require highly skilled personnel
readers of this manual may want to pursue
working with complex and expensive equip-
specific subjects, a list of the more readily
ment. Good equipment and technical exper-
available texts and periodicals published in
tise are essenti,al to a high quality survey.
English follows. Some of them date back as
Attempts to use obsolete or “cookbook” in-
many as 30 years, and parts of these are out-
terpretation methods in geophysical surveys
dated. Nevertheless, much of the theory pre-
often increase the total cost of the survey
sented in them is still valid today.
and result in an inferior product.
Some geophysical data can be used direct-
ly in geologic interpretations. Other geophy- Elementary Textbooks Iof a
sical data require considerable processing be-
General Nature
fore the data can be interpreted, and the cost
of data reduction is a major part of the total Dobrin, M. B., 1960, Introduction to Geo-
cost of the survey. Many data processing op- physical Prospecting: Second ed., Mc-
erations in use today require the use of Graw-Hill Book Co., Inc., New York,
electronic computers. 446 p.
APPLICATION OF SURFACE GEOPHYSICS 3
Eve, A. S., and Keys, D. A., 1966, Applied rent Resistivity Prospecting : Gebruder
Geophysics in the Search for Minerals : Borntrleger, Berlin, 103 p. 1 1*
Fourth ed., Cambridge University
Press, London, 382 p. Books Emphasizing the Seismic
Griffiths, D. H., and King, R. F., 1965, Ap- Method
plied Geophysics for Engineers and
Geologists : Pergamon Press, London, Dix, C. H., 1952, Seismic Prospecting for
223 p. Oil : Harper, New York, 414 p.
Nettleton, L. L., 1940, Geophysical Prospecti Musgrave, A. W., ed., 1967, Seismic Refrac-
ing for Oil : McGraw-Hill Book Co., Inc., tion Prospecting: Sot. Explor. Geophyi-
New York, 444 p. sists, Tulsa, 604 p.
Parasnis, D. S., 1962, Principles of Applied Slotnick, M. M., 1969, Lessons in Seismic
Geophysics: Methuen, London, 176 p. Computing : Sot. Explor. Geophysicists,
Tulsa, 268 p.
White, J. E., 1966, Seismic Wav+Radia-
Advanced Textbooks of a tion, Transmission, and Attenuation :
General Nature McGraw-Hill Book Co., Inc., New York,
302 p.
Grant, F. S., and West, G. F., 1966, Inter-
pretation Theory in Applied Geophysics :
McGraw-Hill Book Co., Inc., New York, Books Emphasizing the Magnetic
681 p. Method
Heiland, C. A., 1940, Geophysical Explora-
tion, Reprinted 1963: Hafner, New Hansen, D. A., Heinrichs, W. E., Jr., Holmer,
York, 1,013 p. R. C., MacDougall, R. E., Rogers, G. R.,
Jakosky, J. J., 1950, Exploration Geophysics: Sumner, J. S., and Ward, S. H.; eds.,
Second ed., Trija, Los Angeles, 1,195 p. 1967, Mining Geophysics, Vol. II,
Land&erg, H. E., ed., Advancee in Geo- Theory, Chapter III: Sot. Explor. Geo-
physics : ~01s. 1-13, Academic Press, physicists, Tulsa, 708 p.
New York. Nagata, Takesi, 1961, Rock Magnetism: Rev.
ed., Maruzen, Tokyo, 350 p.
Books Emphasizing the Electrical
Case History Compilations
Methods
European Association of Exploration Geo-
Bhattacharya, P. K., and Patra, H. P., 1968, physicists, 1958, Geophysical Surveys in
Direct Current Geoelectric Sounding- Mining, Hydrological and Engineering
Principles and Interpretation : Elsevier, Projects: European Association of Ex-
Amsterdam, 136 p. ploration Geophysicists, The Hague,
Hansen, D. A., Heinrichs, W. E., Jr., Holmer, The Net.herlands, 270 p.
R. C., MacDougall, R. E., Rogers, G. R., Lyons, P. L., ed., 1966, Geophysical Case His-
Sumner, J. S., and Ward, S. H., eds., tories: Vol. 11-1956, Sot. Explor. Geo-
1967, Mining Geophysics,Vol. II, Theory, physicists, Tulsa, 676 p.
Chapter II: Sot. Explor. Geophysicista, Nettleton, L. L., ed., 1949, Geophysical Case
Tulsa, 708 p. Histories: Vol. 1-1948, Sot. Explor.
Keller, G. V., and Frischknecht, F. C., 1966, Geophysicists, Tulsa, 671 p.
Electrical Methods in Geophysical Woollard, G. P., and Hanson, G. F., 1954,
Prospecting : Pergamon Press, Oxford, Geophysical Methods Applied to Geologic
517 p. Problems in Wisconsin: Univ. Wiscon-
Kunetz, Geza, 1966, Principles of Direct Cur- sin, Madison, 266 p.
e